Bruce Conner, who has died aged 74, played a significant role in the underground art movement that originated in the US towards the end of the 1950s, though he might have been better known and wealthier had he been less suspicious of the "conservative art gallery system", stayed off the booze and drugs, and concentrated his energies.

Although his work ranged from assemblage pieces - collage sculptures made from nylon stockings, parts of furniture, broken dolls, fur, costume jewellery, paint, photographs and candles, reclaiming objects that had been discarded and neglected - to mysterious mandala designs, photograms of his own body, ink-blot, Rorschach-like drawings and avant-garde films, all had a blend of humour, iconoclasm and intransigence.

Always afraid of selling out, Conner, as a committed oppositional artist, gradually withdrew from the art world in the late 1970s after he became part of the San Francisco punk scene, working as a staff photographer for the "punkzine" Search and Destroy. During that time, he spent most of his nights at a club called the Mabuhay. "I lost a lot of brain cells at the Mabuhay," he explained. "What are you gonna do listening to hours of incomprehensible rock'n'roll but drink? I became an alcoholic, and it took me a few years to deal with that." Yet, despite the woozy atmosphere, he delivered sharp and characterful photos.

Conner was born in McPherson, Kansas. He attended Wichita University, then graduated with a BA in fine arts at the University of Nebraska, where he met Jean Sandstedt, whom he married in 1957. He won a scholarship to the Brooklyn Museum art school and then spent a year on an art course at the University of Colorado, which he flunked. The couple moved to San Francisco, where Conner got involved with the beat generation, before moving to Mexico for two years because "it was cheap". It was there that he found magic mushrooms with his friend, LSD guru Timothy Leary. However, he and his wife ran out of money and returned to San Francisco.

Influenced by dada and surrealism and the found objects of Marcel Duchamp, Conner first gained attention with his assemblage art, exhibiting at the Alan gallery in New York. His movie-making dated back to when he ran a film society at the University of Colorado. He invited Stan Brakhage to show his experimental films there, and Brakhage advised Conner to make films. The consequence was Movie (1958), a 12-minute collage of stock or found footage which moves from the comic (crazy races, a chase scene involving cars and cowboys) to the disturbing (shivering refugees, an execution, air crashes), questioning the way we view a film.

There are 2,000 images in the four minutes of Cosmic Ray (1961), which cuts together footage of fireworks, atom bombs, Mickey Mouse and nude dancing girls, all to Ray Charles singing What'd I Say on the soundtrack. With money from the Ford Foundation, Conner made a number of very short films over the next few years, precursors, for better or worse, of the pop video and MTV.

Easter Morning Raga (1966) was designed to be run forward or backward at any speed, or even in a loop to a background of sitar music. Breakaway (1966) showed a dancer, Antonia Christina Basilotta, in rapid rhythmic montage. Report (1967) dwells on the assassination of John F Kennedy. The found footage exists of repetitions, jump cuts and broken images of the motorcade, and disintegrates at the crucial moment while we hear a frenzied television commentator saying that "something has happened". The fatal gun shots are intercut with other shots: TV commercials, clips from James Whale's Frankenstein and Lewis Milestone's All Quiet on the Western Front. The film has both a kinetic and emotional effect.

Paradoxically, the critical success of these films and the interest they created did not please Conner. "I've always been uneasy about being identified with the art I've made," he stated. "Art takes on a power all its own and it's frightening to have things floating around the world with my name on them that people are free to interpret and use however they choose." In fact, he decided to make a film "to ruin my reputation as a film-maker". It was called Leader (since destroyed) and consisted of a dramatised recording of American soldiers captured by the Nazis in which Conner highlights the phrase "We've gotta get out of here" by repeating it multiple times in the hope that the audience would act accordingly.

In 1967, he had his first experience of commercial film-making when he shot a 14-minute film on location during the making of Cool Hand Luke, starring Paul Newman, in which his friend Dennis Hopper had a small role. It was released unedited (Hopper claimed that "much of the editing of Easy Rider came directly from watching Bruce's films").

Conner continued to make his own short films including Crossroads (1976) in which the 1952 atomic bomb test at Bikini Atoll becomes a thing of terrible beauty when shown in extreme slow motion from 27 different angles. As countercultural as ever, one of his last films was America Is Waiting (1981), which lampoons US military might to a song by Brian Eno and David Byrne.

He is survived by Jean and their son Robert.

• Bruce Conner, artist and film-maker, born November 18 1933; died July 7 2008